Telephone system



H. w. MACDOUGAL AND H. D. MAQPHERSON.

TELEPHONE SYSTEM. APPLICATION FlL ED JULY 31, 1919- I I 1,387,284, Patented Aug. 9, 1921.

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TELEPHONE SYSTEM.

APPLICATION HLED JULY 3!, I919- PatentdAug. 9,1921.

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by M A7734 H. W. MAcDOUGAL AND H. D. MAcPHERSON.

TELEPHONE SYSTEM.

APPLICATION FILED JULY 31. I919.

1,387,284. Patented Aug. 9,1921.

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H. W. MACDOUGAL AND H. D. M'AcPHERSON. TELEPHONE SYSTEM.

APPLICATION FILED 'JULY 31, I919- 1,387.-,'284. Patented Aug. 9,1921.

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. Hugh .0. MacP/verson by M ny H. W. MAcDOUGAL AND H. D. MACPHERSON- TELEPHONE SYSTEM.

APPLICATION FILED JULY 31.1919.

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Patented Aug. 9, 1921.

UNITED; STATES PATENT OFFICEQ 1 HARRYW. MAcDOUG-AL, 0E EAs'r ORANGE, A D HUGH n. MAQPHERSON, or MAPLE- WOOD, NEW JERSEY, AssrGNoEs T0 WESTERN LECTRIC COMPANY, INCORPO- RATED, on NEW YORK, N. Y., A coE-PoEAT'IoN. or NEW YORK.

' TELEPHONE SYSTEM.

To all'whomitmag comm; 3 Be it known that we, IIARRY'VV. MAG- DOUGAL and HUGH D. MAcPHERsoN, citi zens of the United States, residing at East Orange, in the county-of Essex and State of New Jersey, andat Maplewood, in the county of Essex and State of New Jersey,

respectively, have invented certain new and useful Improvements in Telephone Syslines extending between widely separated stations are controlled over asinglesignal ing path common to suchtrunk lines.

In systems of this character it has been" proposed to employ at opposite ends of the signaling path, signal sending means for,

' transmitting over the signaling path code signals individual to the different trunk lines and determined by the trunk line in signaling condition. l r

The, object of the present. invention is to provide improved means for determining and setting up the difierent'code signals to be transmitted bythe signal-sending means,

for determining the order inwhich the code signals areset up andtransmittedand for transmission of twocode signals.

In attalning the-ch sel; of this rnventlon,

preventing the simultaneous setting up and each signal sending distributer, which may preferably take the form of an intermitand that many such circuits and lines may be and usually-are provided, in actualv tently operating distributer of the startstop' type generally employed in printing telegraph systems, has associatedtherewith a switching device common to the trunk lines and comprising a plurality of stationary contacts dividedinto groups, each group consisting oi one or more contacts for each trunk line and a cooperating movable contact for each group of stationary contacts,

Specification of Letters Patent.

Patented is. 9, 1921.

" Application filed Ju'1y31', 1919; Serial No. 314,503.

For a more complete understanding of this invention reference should be had to the followingdescription considered in connection with the accompanying drawings,

in which Figuresl to 5 inclusive, when art rangedinthe manner indicated in Fig. 5, represent a system containing one embodiment of this invention; Referring to Fig.

all apparatus shown to the left of the dotted line 2-2 is located at an office X, and that shown between the dotted lines 2 2 and 33 is located at an oifice Y, while' that shown to the'right of the dotted line '8,-3 is located-atanoflice Z. Like apparatusat the two oflices X and Y will be designated by the, same. reference characterswithout primes at the office X and with primes at the ofiice Y. 4 I i Referring to the" drawings there is shown a toll trunk line Ll comprising two talking conductors extending from a central office X to a central ofiice Y. At central office X there is located a toll cord-circuit F by means of which connection is established with the trunk line L1. The trunk line L1 mayv be connected with a toll switching trunk circuit M extending from the central office Y to the central ofiice Z, at which ter minates a subscribers telephone line N with which'the toll switching trunkcircuit M ing trunk, and one subscriberls telephone line areshown, it is to be understood that this 15 for the purpose of conven ence only,

service.

, The signals for a plurality of toll trunk lines may lee-controlled over a signaling.

well-known -manner for duplex operation,

for which purposethere is provided at the ends of the conductor artificial balancing lines AL and differential polarized relays 25 and 25. Each end of the common signaling conductor P is connected with a commutator for sending and receiving signals. These commutators are preferably of the well-known start-stop type of distributers employed in connection with printing telegraph systems and are, it will be understood, provided with a synchronizing device (not shown) by means of which approximate synchronism is automatically maintained therebetween.

The commutator at oflice X comprises a sending distributer S for transmitting sig nals over conductor P to the office Y and a, receiving distributer R for receiving signals transmitted over conductor P from the ofiice Y, and similarly the commutator at the oflice Y comprises a sending distrihuter S and a receiving distributer R forftransmitting signals to and receiving signals from. the office X over the conductor "P. These commutators comprising sending and. receiving distributers are of the same construction and a description of one will be sufficient. For convenience, the construction of the sending and receiving distributers S and R only will be described for the sending and receiving distributcrs S and R are exactly like the former and need no specific descrip tion. The sending and receiving distribuend so that each brush controls two sepa-" rate groups of circuits.

Between the common shaft and each brush there is provlded friction clutch mechanism brush when released. .The face of thesending distributer S is stationary and 1s provided with a common sending ring 14, a

restoring segment 7, a start segment 8 andindividual sending segments 1 to 6 for controlling thesignals transmitted over the signaling conductor P and with a common ring 15 and segments 16, 17 and 18 for controlling local circuits. The face of the receivlng distrlbuter R is also stationary and is provided with a common receiving ring19 and individual receiving segments 1' to 6 for selecting a circuit according to the code of signals received over the signaling con ductor P, segments 20 and 21 through which the selected signal receiving circuit 'is com pleted, segments 22 and 23 for controlling the circuit of the associated release magnet REM and a ring 24 and segment 31 for controlling a local circuit.

(not shown) by means of which the constantly rotating shaft causes the rotation of each At central office X the common conductor P is connected to the common sending segment 14 While the normal contact of the differential polarized. relay 25 thereat is connected with the common receiving segment 19, and the alternate contact is connected with the segment 22in suchmajnner that when the relay 25 is operatively energized, the release magnet REM is energized to release the brush 10. At the central oflice'Y the common conductor P is connected with the common sending segment 14: while thenormal contact of the differential polarized relay 25 is connected with the common receiving segment 19', and the alternate contact of this relay isconnected with thesegment 22 in such manner that when the relay 25' is operatively energized, the release magnet RRM is energized to release the brush 10.

The signals transmitted over the common signalingconductor'P'by the sending distributers S and S are determined by the polarity of current connected with the individual sending segments of the respective sending distributers S and S". These polarities are determined by the position of the brushes offautomatic selector switches G and G provided at the respective oiiices X and Y. These automatic selector I switches which are common to aplurality of trunk lines, are alike in structure. The automaticwselector switch G is provided witheight brushes a, b and 1 to 6 mounted upon a single shaft driven by a'motor magnet MMinitially controlled by a start magnet 30 connected in the start conductor or lead ST common to the trunk lines. Brushes -1 to 6 are connected directly with the respective individual sending segments 1 to 6 of the sending distributer S. Brush a is connected with one winding of a relay 32 whichcontrols the stopping of the motor magnet MM and the energization of the release magnet SRM of the sending distributer S; Brush 6 is connected'with a "contact of relay 32. for the purpose of assisting in thecontrol of the switch as will more fully hereinafter appear. A slow releasing relay 33 and: a release relay 34 associated with theautomatic selector switch G are controlled by the sending distributer S for reasons which will more fully hereinafter appear. A plurality of contacts equal to twice the number of toll trunk lines to which the automatieselector switch G is common is associated with each brush. The contacts associated with the different brushes are mounted at diiier'ent levels in position: to be engaged'by the respective brushes as they are rotated by the motor magnet MM. Two correspondingly positioned contacts of all levels are allotted to each trunk line, for example, the first two contacts maybe allotted to trunk line No. 1. the second two to trunk line No. 2, the third two to trunk line No. 3, etc. The two con tacts of the levels (rand Z) allotted to each;

trunk line are connected with relays individual to and associated with the outgoing end of thetrunk line. The trunk line Ll represented in the drawings maybe cone sidered as trunk line No? l. "As-shown, re lays individualto'the outgoing end ofthis trunk line Ll a're connected by'means of individual signal control leads Al and Cl and restoring leads B1 and D1 withthe allotted contacts of levels a and Z), signal control leads A1 and being connected tolthe re-I' spective first and second contacts of level a and conductors Bland D1 to'the respective-j distributer Rf. transmitted from a particular indivldual sending s'egment,-'the lock-up relay", connected the common signaling conductor VP.

"ciated with the incoming ends of the trunk lines by means of three individual conductors and a common conductor. This switch G is associated with the trunk line L1 shown in the drawings by means of the in-' dividual signal contro'lleadsAl and U1 and restoring lead 'BDl and a common start lead ST, individual leads Al and Cl being connected with the'allotted first and secondf'contacts of level a, individual lead BDl'with both allotted contacts of level '1) and the common conductor with the start mag 'netBO ofthe switch G; The selector switch Gis associated with each of the other trunk lines through 1 similar signal control and restoring leads A, C and BD. The polarities'con-necte'd with the individual sending segments'lf to 6 of the sending distributer S are determined'by the position of the brushes: 1 to 6 of the' 'switch Gr, and the different "combinations of polarities connect'ed with the allotted first and second con 95 r tactsof the levels o ne to six forthe vari ous trunk lines are identical with those connected with the" automatic selector switch G. These are shown in the preceding table.-

- In o'rderthat the signals transmitted from theioffice X, by the sending distributer S and receivedat the ofiice Y may be utilized,

there are provided thereat six locking relays 41' to 46* inclusive having energizing windings connected with the respective individual re'ceiving'segments 1 to 6 of the receiving lfVh'en' a negative signal is with'the corresponding individual receiving segment will be energized and locked'up. c L'oclg-up're'lays ll"to l lcontrol a plurality 3 ofjreceiving 'and' se'le'cting relays 50 to 64: inclusive, which cooperate with lock-up re a V -1l5 9 dividua-l toa 'trunkl'ine,"while lock-up relay" lay 4:5" to select asignalcontrol circuit in tGTCoritrols the polarity of current connected with the selected signal control circuit. The individual s gnal -"0 tro1 circuits are" connected with 'co'ntacts ojfthe relays "'57 to 64 -inclusivef Similar equipment is" providd" at'the centralolfice 'X for utili'zinglthe signals transmitted [from the o'fiice over *Having in mind this brief description be the apparatusof the system shown in the I drawinga'ieis thought that the invention a will be more thoroughly understood from a description of the operation of the system shown.

Gomwction of 00rd circuit F with trunk Zine L1.

The operator at office X desiring to estab-. lish connection with the telephone line N which terminates at office Z, connection with which must be established through the oflice Y, communicates with the operator at office Y over an order wire circuit (not shown). The operator at the office X ascertaining from the operator at office Y that the connection with the telephone line N is to be completed by way of the trunk line L1, inserts calling plugof cord circuit F into jack 71 of the trunk line L1. Relay 73 thereupon operates over a circuit from battery through the winding of marginal relay 72, sleeve contacts of the plug 70 andthe jack 71 and the winding of relay73 to ground. Relay 72 is marginal and does not operate at this time. Relay 73 in operating causes the energization of relays 74 and 7 5,

relay 74 operating over a circuit from battery through the contact of relay 73, winding of relay 74 and the normal contact of relay 76 to ground, while relay operates over a circuit from battery through the contact of relay 73, winding of relay 75 and the normal contact of relay 77 to ground. Relay 74 in operating establishes a locking circuit for itself through one of its contacts to ground, and causes the energization of a differential relay 7 6 over a circuit from battery through the left-hand winding of relay 76 and an alternate contact of relay 74 to ground. Immediately upon energization relay 76, by the closure of its inner left-hand contact is locked up independent of relay 74. Relay 74 in operating causes the energization of the start magnet 30 over a circuit from battery through the start magnet 30, common start lead ST, middle normal contact of relay 78, right-hand normal conf tact of relay 79 and right-hand alternate contact-of relay 74 to ground. jStart ma net 30 closes the circuit of the motor magnet which is of the self-interrupting type. The

motor magnet advances all brushes of1 the selector G step-by-step until the brush aengages the contact to which the signal control lead A1 is connected. This signal control lead Al was previously grounded by the energization of relay 74 so that upon the engagement of the brush a with the first con.-

tact assigned to trunk line L1, relay 32 op-H erates over a circuit from battery through the upper winding of relay 32, brush a, signal control leadAl, left-hand normal con-X tacts of relays 78 and 79, and an alternate contact of relay 74 to groimd. Belay 32 in operating opens the operating circuit of motor magnet MM thereby stopping the advancementof the brushes of the selector G;

- The relay 32 also completes a locking cir cuit for-itself which may be traced from bat; tery through the contact of relay 34, the middle alternate contact and the lower winding of relay 32 to ground. The operation.

tact of relay 79 and an alternate contact of;

relay -74 to ground. Relay 78 in operating removes the ground from signal control lead A1 connected thereto by the operation of re- -lay 74. thereby opening the energizing circuit of I relay .32, which, however, remains operated due to the closure of its locking circuit; Relay 32 in closing its-lower contact causes'the energization of the releasemagnet SRM over a{ circuit from battery through ring 15, brush 9 and segment 16 of the sending distributer S, the lower contact of relay 32 and the winding of relay magnet Sid-M to ground- The attraction of the armature of the release magnet. SRM upon the energihation thereof releases the brush9 which is thereupon rotated through a complete cycle at" Leo polarities, it"will be observed that at the stopping of the automatic selecting switch Gr with the brushes thereof in engagement with the first of the two contacts alloted to trunk line L1, positive current is connected with such first contacts on the first, second,

fourth, fifth and sixth levels, while negative A current is connected with such first contact of the third level. When the brush 9 engages segment 17, slow releasing relay 33 operates over a circuit from battery through 6, currents of the polarity connected with these segments are successively connected with theconductor P. "When brush 9 moves 7 'out of engagement with segment. 17, the

energizing circuit or the slow releasing rethrough seginent, brush 9, segment 18 and the winding ofthe release relay 34 to ground. The energization of release'relay 34 opens the locking circuit of relay .32 whereupon .this relay releases. Relay 33is made slow in releasing so that its contact remains open until after the .opening'of the release .relay 34: is deen'ergi zed.

contact of release relay 34:. As the brush 9 moves out of engagement with segment 18, When brush 9 engages restoring segment 1" negative current is connected with the common signaling conductor P. The automatic. selecting switch G is now in condition to be seized by another trunk line, since the trunk line L1 is disconnected therefrom and the sending distributer S isin normal condition.

The connection of positive current through start segment sflwitli conductor P causes the operation of the diiierential polarized relay 25. at .oflice Y over a circuit from positive battery through segment a, brush 9, common sending ring ll'and the junction point between t'lieavindings of diftactof relay 92 which is not energizeduntil ferential polarized relay 25, thenby one path through the lower'winding of relay 25 5 and artificial line to .ground and by another I path through the upper winding of relay 25,

conductor P, .bothlwindings of the differem tial polarized relay 25, "and the artificial line to ground. 1 The operation otrelay 25 causes the energization: of release magnet 'RRM over a circuit from-battery through the alternate contactof relay 25, segment 22, brush 10, segment 23and the winding of release magnetRiRM to ground. The

attraction of the armature of the release magnet RRM upon the eiiergization thereof releasesthe brush 10" which is thereupon ro tated through a complete cycle at the end or which the brush is stopped in its normal po- 'SitlOlL As the brush lOinoves out of engagement with the segments 22 andv 23, the release magnet RRM' is deenergiz'ed and permits the restoration of its armature t5 "normal position'preparatory to stopping the brush when it reaches its normal position. When the brush 10"moves out of engageelusive. The armature of the differential polarized relay'25f' remains n its alternate position as long as positive current is coniie'cted with-the other end of conductor P i i p w -d1uctor P, and the energizing circuit of the and moves to its normal position whenever end of conductor. P. The brushes 10" and 9- are being rotated at the same; time and while brush 9 1s n engagement with segment '3, to which negative current iscon- 25, common receiving ring 19, bruslr10',*=

individual receiving segment 3 and the lower winding of relay 4L3 -to ground. 5Relay 43 then locks up through its upper winding and contact and the contact of'relay 82, and causes the operation of relays 51 and 52 over a circuit from battery through windings of relays 52 and 51 and V the lower contact of relay 43 to ground. When the brush 10 engages segments 20 over a circuit from negative battery 86 through the normal contact of relay46, seg- -ment 20, brush 10', segment 21, normal contact of relay 45, lower normal contact of relay50", lower alternate contact of relay 51, upper normal contacts of relays53 and hand winding of relay .85 to ground. Relay 93 is energized in parallel'with relay 85'but does not lock up on account of the openconafter the locking up of relay 85 and there- 1 lease of relay 93. The eiiergization of relay 93 at this time performs no useful function.

Relay 85, in operating, completes alocking circuit for itselfv from batteryv through its right-hand alternate contact and right-hand winding toground. -The operation of the relay '85 individual to. the incoming end 03E the trunk line L1 causes the lamp 90' to be lighted overa circuit from battery through 4 tlie right-hand alternatecontact of relay 85, "lower normal contact of relay 91-..and' the 1 lamp 90 to ground. Relay 85 in closing its left-hand alternate contact connects super visory relay 94 in circuit with the talkingv conductors-of thetrunk line L1 extending toward the plug.- WVhen the brush .10" moves out of engagement with the segments 20 and 21, the energizing circuit of relays 85 and 93 is opened causingthe deenergization-of relay 93. Slow releasing relay 92 is thenenergized over a circuit'irom battery and 21, signal receiving relay operates" -58, selected signal receiving conductor -E'1' individual to trunk lineLl, EtlICl'lZhB leftiio through the right hand alternate contact of relay 85, right-hand normal contact of relay 98 and the winding of relay 92 to ground. NVheii the brush 10 engagesthe segments 22 and 23', the armature of relay :25 is in its normal position since brush 9 is connected with restoring segment 1" and negative currentis connected with the conreleasemagnet RRM' will be open. The ention should be established.

gagement of the brush 10' with the segment dition, so that it may be associated with any other trunk line. The lighting of the lamp 90 serves as a guard signal to the operator at the ofiice Y, indicating that the operator .at the oflice X has connected the toll'cord J circuit B with the proper trunk line L1.

Connection of toll switching trunk time M with telephone line N At the time the operatorat the office Y designated the trunk line with which the operator of office X should connect the cord circuit F, the operator at the office Y also communicated with the operator atthe otfice Z over an order wire circuit .(not shown) advising the operator at theofiice Z the number of the desiredline, whereuponthe operator at the office Z designatesthe toll switching trunk circuit over which connec- Assuming toll switching trunk circuit M to be that desig nated, the operator at the oflice Z, after' designating this trunk, inserts plug 100 of the toll switching trunk circuit M into jack 101 of the telephone line N. Relay 102 and cut-ofi relay 103 thereupon operateover a circuit from battery through the winding of relay 102, sleeve contacts of the plug 100 and the jack 101 and the winding'of cut-oft relay 103 to ground. The energization of relay 102 causes supervisory lamp. 104 to be lighted over a circuit from battery through the lamp 104, lower alternate contact ofrelay 102, resistance 105 and the normal contact of relay 106 to ground. The operation of cut-0H relay 103 disconnects line relay 107 from the line wires of the telephone line Y.

Connection of tmmlc Zine L1 with tall switching tmmk circuit M.

normal contact of relay 108, tip contacts of? thejack 111 and theplug 110, upper alter nate contact of relay91, upper normal contact of. ringing relay 114, winding of supervisory relay 94, left-hand alternatecontact of relay 85, lower normal contact ofringingii ilrelay 114, ring contacts of the'plug 110 and the jack 111,'the right-hand normal contact of relay 108 and the'right-hand winding of relay 106 to ground. The energization of guishes the lamp 104. g

The energization of the supervisory relay 94 causes the energization of relays 116,117, 118 and 119, the energizing circuit for relay of relay 116, and the alternate contact of supervisory relay 94 to ground. The energizing circuit for relays117 and 118 may be traced from battery through the'winding of relay 117, the left-hand normal contact of relay 120, winding and left-hand normal contact of relay 118, left-hand normal contact of relay 119, right-hand contact of re; lay 120, right-hand normal contact of relay relay 94 to ground. Relays117 and-118 upon being energ zed. are locked up over a circuit. from battery through the. winding of relay 117, left-hand contact of relay .120,

winding and middle alternate contact of relay 118 to ground. Theenergizing circuit for relay 119 may be traced from battery through the winding" of relay 119, rightcircuit of relays 117 and118, and completes a locking circuit for itself from battery through the winding and alternate contact of relay 119, left-hand normal contact of relay 122, right-hand normal contact of relay relay 106 opens the circuit of and eXtin-J.

a 116 being from battery through the winding 1 121 and the alternate contact of supervisory 121 and the alternate contact of supervisory,"

relay 94 to ground. The energizing circuits for relays 116, 117,118 and 119 are closed simultaneously and. the energization of relay 119 as already explained opens a contact in the energizing circuits of relays.

117 and 118. In order that this contact may not be opened until after relays '117 and 118 have been energized, relay 119. is made slightly slower in operating than relays 117 and 118, but is sufiicientlytast in energizing and de'e'nergizing that it follows the energization and I deenergization of the supervisory relay-94. Theenergizationof relay 118 causes the operation'of'relay 123 over a circuit from battery through the righthand alternate contact of relay 85, winding of relay 123, left-hand normal contact of relay 124 and the right-hand alternate contact of relay 118 to ground. Relay 123 in closing its contact prepares an energizing circuit for relay 124, which, however, as long as relay 118 is energized, is short-circuited by the lefthand normal contact of relay 124 and the right 'hand alternate contact of relay 118. Relay 118 in closing its left-hand alternate contact grounds the signal control conductor Al connected withthe first of the two contactson level a of automatic select- :ing switch G allotted to trunk line L1. The

'pletes a locking circuit through its left-hand winding and in closing its right-hand alternate contact causes the energization of relay 120 over a circuit from battery through the contacts of release relay 34 and slow ereleasing relay 33 right-hand alternatecontact of relay 32, brush 5', restoring conductor BD1 and the winding of relay 120' to ground; Relay 120 upon being energized opens the locking circuits of relays 117 and 118. The resulting deenergization of relay 117 opens the energizing circuit of start magnet 30. The opening of the left-hand alternatecontact of relay 118 removes the ground connection from the'signal control conducter A'l, The opening of the righthand alternate .contact of relay 118 upon the de'e'nergization thereof removesthe shortcircuit about the winding of relay 124, which thereupon operates over a circuit from battery throu h the right-hand alternate con tact of re ay 85,. winding-and contact of relay 123, winding of relay 124 and the lefthand normal contact of relay 121 to ground. The closure of the left-hand alternatecon tact'ozt relay32 causes the energization of the release magnet S'RM of the sending distributer S over a circuit from battery through ring 15, brush 9, segment 16, lefthand alternate contact of relay 32 and the winding of the release magnet SRM to ground.

' The sending distributer thereupon functions to successively connect with thecommon signaling conductorql? currents of the polarities connected 7 w1th the vindividual sending segments of this distributer. The

polarities connected with the sending seg ments 1' to 6 are determinedby the polarities connected with the contactsengaged by the brushes 1 to 6. To restoring segment 1 1", negative current is permanently connected while positive current 1s permanently connectedwithstart segment .9. Since trunk line L1 is the trunk line now involved, posi tive current is connected with segments 1, v2, 4, 5' and 6','wh1le negatlve current 1s connected with'segment 3'. .VVhile the brush 9 is making acomplete cycle, the release magnet SRM is deenergized when thefbrush moves out of engagement with segment 16, the circuit of the slow releasing relay 33 is closed duringthe time the brush is in engagement with segment 17, and the release relay 34 is energized during the time the brush is in engagement with the segment 18, whereby the apparatus. associated with r the sending distributer S and the automatic" selecting switch G functions in the same manner as that associated with the sending dlstributer S and, the automatic selecting switch Gr. Relay 120 becomes denergized upon the energlzat on of the slow releasingrelay 33. Relays- 117 and 118 are not energized upon the release of relay 120, for

the energizing circuit of these relays 117 and 118 is open at thelleft hand normal contactof relay 119 which'is locked up at this time.

nectedinthe common vsignaling conductor P at the'ofllceX operates when the brush 9 engages thestartsegment s, whereupon i the release magnet RRM- of the receiving distributer R is energized to release the brush 10. WVhenthe brush 9 later engages the sending segment 3'," the relay 25 is deenergized, whereupon relay 43 energizes over a circuit from battery throughthe nor-' mal contact-of relay 25, common receiving segment 19,-;brush 10, ndividual receiving segment 3 and the lower windlng of relay 43 to ground. Relay 43 thereuponlocks up through its upper winding andcontact and the contact of the now denergized relay 82.

.Relays 51 and 52 operate uponther energizatio'n ot relay 48. Later upon the engagementof the brush 10 with segments 20 and 21, relay 7 7'operates over a circuit fromnegative battery 86 through the lower nor-' malqcontact of relay;46, segment 20, brush 10, segment 2l,-lower normal contacts of 95 The differential polarized relay 25 con i relays 45 and 50, lower alternate contact of relay 51, upper normal contacts of relays '53 and 58, signal receiving conductor E1 and the left-hand winding of signal receiving relay 77 to ground. Relay 77 thereupon locksup through its right-hand winding and right-hand alternate contact, opening the energizing circuitof the slow releasing relay 7 5, and nectlng this resistance in parallel with the grounds resistance 130, thereby con- 'Winding of relay 73. The resistance of the circuit including the Winding of the marginal relay 72 is thereby reduced to such an extent that the relay 72 operatesto light the supervisory lamp 131. When brush 10 of the receiving distributer R reaches its normal position relay 82 is operated Whereupon relays 43, 51' and 52 are restored to their normal condition. The lighting of the supervisorylamp 131serves as a-signal to the operator at the ollice X that the connection has been completed through to the line of the Wanted subscriber and that the established circuit is in condition for signaling the subscriber oi the wanted line.

Operator at 077506 X actaates ringing key.

The energization of relay 7 9 opens the lock- 1 ing circuit 01 and causes the release of relay 7S. Operator at 0 #506 X restores ringing keg J Upon the restorationof the ringing key 132 to normal positionrelay 134 releases,

causing the deenergization of relay 79, thereby closing its left-handcontact to ground the signal control conductor A1. The'deenergization ot relay Z8 followed by the. de

energization of .relay79 reestablishes'the energizing circuit for the start magnet 30,

WhGIGUPOI). the :automatic selector switch Gr and the sending 'distributer S tunctionin the same manner as when the plug 70 Was inserted into the'jack 71 transmitting the same combination of impulses over the common signaling; conductor P. 1 The receiving distributer R also functions as before'to receive and distribute the" combination-of impulseswvhereby the relay S2 is released, relay 43 energized and locked up and relays 51 and 52 operated. Then when the brush- 10 engages the segments and 21, signal receiving relay 93 operates due-to animpulse over a circuit from negative battery 86, through the normal contact of relay 46,

contacts 01 relays and 50, lower alternate contact or relay 51, upper normal con tacts of relays and 58, signal receiving conductor El and the right-hand Winding of signal receiving relay 93 to ground. Relay 93 immediately locks up overa circuit from battery through its left-hand Winding and lett-bandalternate contact and the contact of relay 92 to ground. The opening of the right-hand normal contact of relay 93 opens the energizing circuit 01"- the slow release relay 92, Whilethe closure of the righthand alternate contact of relay 93 causes the .energization of the slow release relay 13 over a circuit from battery through the and 93 and thewinding of relay 135 to ground: Relay-135 inoperating causes the operation of a sliow release relay 136 and ringing relay .114, these relaysoperating in parallel upon theclosure of theuright-hand contactot' relay 135. The opening of the normal contactsotringing relay 114 causes 2 the jdenergization of supervisory relay'94, but relays 116, 119, 123 and 124 do not release for they are held operated through the contact of relay 136 which is energized While the ringing relay l14is energized: The opening of the'contact of relay 92uponthe dull releasethereotopens the locking circuit of. relay 93 Which thereupon releases. The openingot the right-hand alternate contact of relay'93 causes the release of the slow releasing relay 135'Wl1l6l1 l11 opening its right-hand contactopens the energizing circuit ofringing relay 114 and slow releasing relay 136. 'Ringing relay 114 releases betorerelay 136 and upon'the closure'ot' the normal contacts of this ringingrelay 114, "supervisory relay '94-is immediately ener- -'opened until after the closure 0t the-alternate contact of the supervisory relay 94.

' lVhile ringing. relay 114'is energizeththe source of ringing ourrent 137 is connected right-hand alternate contacts of relays 85 gized. 'The contact ot relay 136' is not with the toll switching. trunk circuit M to i1 caluse the energization ot' ringing "response relay 138. i l fhile the energizing -circuit ot relay 1106 sopened bygthe opening of the normal contacts of ringing relay 114, relay 106 does not have time to close its normal contact before the closure of the upper alternate contact of the ringing relay 114, 1 when a temporary holding circuit for relay 106 is completed from battery through the left-hand winding of relay 106, .left-handf normal contact of relay 108, tip contacts of the jack 111 and the'plug 110, upper alternate contact of relay 91 and the upper alternate contact of ringing irelay 114 to grour'id. The response of relay 138 causes the operation oi" relay 108 and ringing segment 20, brush 10 and segment 21 of: the receiving distributer R, lower normal lamp 104 is not lighted during the energizayt'ion of the ringing relay 114. "Upon energiaation ringing'relay 139 connects the source of ringing current 140 with the line -ot subscriber' ll to'r causing the operation of pulse from battery 99 with the original energizing circuit of relay 7 7. The relation of the number of turns of the two windings of signal receiving relay 77 issuch'thatwhen positive current traverses the left-hand or; energizmg winding of this relay at the same time that negative current is traversing the right-hand or looking winding the relay'is diiferentialized and releases its armatures. The opening of the left-hand alternate contact of this relay disconnects the resistance 130 from parallel relation with the winding of relay 73, whereupon the marginal relay 72 releases its armature and extinguishesthe lamp 131. Relay 77 inoperating also causes the operation of the slow release rela 1 75, restoring the apparatus at the ofiice 1. to the same condition as it was prior to the insertion of the plug 110 into the jack 111.

The extinguishment of the lamp 131 serves, as a signal to the'operator at the oflice X that the wanted subscriber has responded.

Subscriber restores receiver to switchhoolc.

118 and 119 in the mannerbefore described,

causing the movement of the automatic selector switch G until its brush a engages the grounded signal control conductor Al, when the sending distributer S transmits over the conductor P, the same combination of impulses transmitted when the plug 110 was inserted in the jack 111. The operation of relay 118 also causes the energization of relay 123. Relay 120 also operates when relay 32 is energizedto release relays 117 and 118. Upon the release of relay 118,

relay 124 operates. Upon the return of the brush of the sending distributer S to normal position and the release of relays 117 and 118, the automatic selector switch G and the sending distributer S are freed from the trunk line L1 and may thereafter be temporarily associated with any other trunk line. The transmitted combination'of impulses is received at the oflice X through the action of the relay 25 and the receiving distributer R causing through the energization of relays 43, 51 and 52 the energization and locking up of signal receiving relay 77 in the manner previously described. Resistance 130 is thereupon connected in parallel with the winding of relay 73 to cause the operation of relay 72, whereby the supervisory lamp 131 is lighted to furnish a disconnect signal. Relay 7 5 releases upon the energization of relay 77. Following the energization of relay 77, the brush 10 is stopped in its normal position and relay 82 is energized causing the deenergization of relays 43, 51 and 52.

Operator at ofiice X disconnects toll cord circuit F from trunk ZZ'TLGHLI.

The operator at ofiice-X upon observing the lighted condition of the supervisory lamp 131 withdraws the plug from the jack 71., causing the release of relays 72, 73, 74 and 78. The release of relay 72opens the circuit of and extinguishes the supervisory lamp 131. The release of relay 74 causes the energization of start magnet 30 over a circuit from battery through the winding of start magnet 30, start lead ST, outer right-hand alternate contact of relay 76 and the righthand normal contact of relay 74 to ground. The deenergization ofrelay 74 also grounds signal control conductor C1 connected with the secondof the two terminals on level a of the selector switch G allotted to trunk line L1. Motor magnet MM functions upon the energization of the start 'magnet 30 to advance all brushes of the selector switch G until the brush a engages the contact to which signal control conductor C1 is connected, whereupon the relay 32 operates and locks up, opening the circuit of the motor magnet. The operation of relay 32 completes a circuit through the right-hand winding of relay 76 which may be traced from battery through the contacts of relays 34 and 33, upper alternate contact of relay 32, brush 5, restoring conductor D1" and the inner right-hand alternate contact and righthand winding of relay 76 to ground. This relay 76 thereupon becomes difierentialized and releases its armatures. Brushes 1, 2, 4 and 5 of the selector switch G now connect positive current with individual sending segments 1, 2, 4 and 5 of the sending distributor S, while brushes 3 and 6 connect negative current with the individual sending segments 3 and 6. The closure of the lower alternate contact of relay 32 energizes the release magnet SRM of the sending distributor to release the brush 9, which. in making a complete revolution, transmits over the commonsignaling conductor P a combination of impulses corresponding to the polarities connected with the individual sending segments of the distributer. The

transmitted impulses are received at the the usual call bell 1 11 at the station. Upon the release of relay 11%: ringing current from the sourre 1 is disonnected from the-toll switching trunk circuit M and ringing response relay 138 releases, causing the deen ergization of relay 108 and ringing relay 139. The release of relay 108 connects both windings of relay 106 in circuit with the supervisory relay 9 1 before the holding circuit of relay 106 is opened at the alternate contact of relay 108, whereby this relay 106 remains energized. The deenergization of relay 139 disconnects ringing current from the source of current 1610 from the line of subscriber N.

Subscriber of telephone Zine 1V removes rccewcr from s-wtchhoolc.

The subscriber at the station on telephone line N in responding to the operation of the call bell 1 11 removes the receiver from the switchhook, thereby causing the operation of supervisory relay 1 15 over a circuit from battery through the winding of supervisory relay 1&5, upper normal contact of ringing relay 139, ring contacts of the plug 100 and the jack 101, out over one side of the line, through the substation apparatus and back over the other side of the line, tip contacts of the jack 101 and the plug 100, upper alternate contact of relay 102 and lower normal contact of ringing relay 139 to ground. Supervisory relay 1 15 in operating causes the energization of relay 108 over a circuit from battery through the left-hand winding of relay 108, contact of supervisory relay 1&5, right-hand winding of relay 108 and the alternate contact of relay 106 to ground. Relay 108 in operating closes its alternate and opens its normal contacts, whereby relay 106 is disconnected from the circuit including the supervisory relay 9 1, and is maintained energized through its left-hand winding and the alternate contact of relay 108. Relay 108 in operating also causes the deenergization of the supervisory relay 941. The supervisory relay 9% in opening its alternate contact opens the energizing circuit of slow releasing relay 116 and the holding circuit of relay 119. Relay 116 is slow in releasing so that before it releases its armature relay 1 16 which is slow to release is operated over a circuit from battery through the winding of relay 146, alternate contact of relay 116 and the normal contact of supervisory relay 9 1. This relay 146,

however, performs no useful function at this time. Upon the closure of the normal contact of relay 116, relays 117 and 121 operate over a circuit from battery through the winding of relay 117, left-hand contact of relay 120, winding of relay 121, righthand normal contact of relay 118, righthand alternate contact of relay 124, normal contact of relay 116 and the normal contact 01? supervisory relay 9a to ground. Relay 121 in operating completes a locking circuit for itself and relay 117 from battery through winding of relay 117, left-hand contact of relay 120 and the winding and right-hand alternate contact of relay 121 to ground. Relay 121 by openingits left-hand normal contact causes the de'energization of slow releasing relays 123 and 124. Relay 121 by closing its left-hand alternate contact grounds the signal control lead Cl which is connected to the second of the two contacts, on level a of the automatic selector switch Gr, allotted to trunk line L1. The energiza tion of relay 117 causes the energization of the start magnet 30 whereupon the motor magnet MM advances the selector switch until the brush a engages the contact to which the signal control conductor C'l is connected. Relay 32 thereupon operates and locks up in the manner hereinbefore described, stopping the motor magnet -M1V1. Relay 120 then operates over a circuit from battery through the contacts of relays 3 1 and 83, right-hand alternate contact of relay 32, brush Z), restoring conductor BDl and the winding of relay 120 to ground.

Relays 117 and 121 are de'e'nergized upon the energization of relay 120.

The brushes of the selector switch G. en-v gaging the second set of contacts allotted to the trunk line L1 connect a current of positive polarity with the individual sending segments 1,;2, 4 and 5,'and current of negative polarity to the individual sending segments at 3' and 6'. The energization of relay 82 causes the energization of the re lease magnet SRM associated with the sending distributer S", whereby the brush 9 is released and makes a complete revolution to transmit over the common signaling conductor P a combination of impulses or code signal determined by the polarities connected with the contacts of the automatic selector switch G engaged by the brushesl' and 6. When the-combination of impulses has been transmitted, the sending distributer S" and the automatic selector switch G and associated. apparatus are restored to normal position, and the relay 120 is deenergized. These transmitted impulses being received at the ethos X, cause the energization and locking up of relays 43 and 16 as the brush 10 of the receiving distrlbuter Ttpasses over the individual receiving segments 3 and 6 thereof. The operation of relay e13 causes the energization of relays 51 and in the manner ll'ereinbe'fore deicrioed. Since relay 46 is energized when brush 10 engages the segments 20. and 21 of the receiving distributer R the signal receiving relayW will be dilferentialized and released. This brought about by connecting a positive imoffice Y by means of the relay 25 and the receiving distributer R, causing the energization of relays 43 and 46 and the looking up thereof through the respective upper windings and upper alternate contacts thereof, and the contact of the deenergized relay .82. Relays 51 and 52 operate upon the energization of relay 43 so that when the brush 10- engages segments 20 and 21', signal receiving relay 85 is differentialized, due to a positive impulse from the positive battery 99, through the lower alternate contact of relay 46, segment 20, brush 10, segment 21, lower normal contacts of relays 45 and 50, lower alternate contact of relay 51, upper normal contacts of relays 53 and 58, signal receiving conductor El and the left-hand winding of signal receiving relay 85 to ground. Relay 85 thereupon releases its armatures. The opening of the right hand alternate contact of relay 85 causes the release of relays 123 and 124, and the closure of the normal contact of relay 85 causes the lighting of the lamp 90 over a circuit from battery through the right-hand normal contact ofrelay 85, lower alternate contact of relay 91 and the lamp 90 to ground. The lighting of the lamp 90 now serves as a disconnect signal to the operator atthe ofiice Y. The opening of the left-hand alternate contact of relay 85 opens the circuit which includes supervisory relay 94 and relay 106, whereupon both of these relays release their armatures. The opening of the alternate contact of supervisoryrelay 94 restores relays 116 and 119 to normal condition. Relay 146 is energizedafter the release of relay 94 and before the release of relay 116, but is deenergized upon the opening of the alter,- nate contact of relay 116. The energization of relay 146 does not at this time perform any useful function- The release of relay 106 of toll switching trunk circuit M causes the lighting of lamp 104 over a circuit from battery through the lamp 104, lower alternate contact of relay 102, resistance 105 and normal contact of relay 106 to ground. The lighting of the lamp 104 now serves as a disconnect signal to the toll switching operator at the ofiice Z. -The op erators at the office Y and the office Z may, I upon, observing the lighted condition of the respective supervisory lamps 90 and 104, withdraw the plugs 110 and 100 from the respective jacks 111 and 101, thereby restoring all apparatus to normal condition.

telephone line 1V recalls operator at 77500 X.

Subscriber on 146 controlled by the supervisory relay are deenergized. Of the other relays associated with the incoming end of the trunk line L1, signal receiving relay 85 and relays 91 and 112 are energized, while signal receiving relay 93, ringing relay 114 and the slowreleasing relays 92, 135 and 136 are deenergized. Relay 116 is made slow in releasing so that its alternate contact will be held open and its normal contact open during the short periods when the alternate contact, of supervisory relay 94 is open while the subscriber of telephone line N is repeatedly opening and closing the switchhook contact to signal the operator at office X. Similarly relay 146 is made slow in releasing so that it holds up during the short periods when the normal contact of-the supervisory relay 94 is open. Relays 122, 123 and 124 are also made slow in releasing to assist in the control of the recall signal before the operator at the oilice X when the subscriber of telephone line N is recalling thisoperator.

Upon the first opening of the switchhook contact at the station, over telephone line N,

supervisory relay 94 is energized, where upon relays 116, 117, 118 and 123 operatev in the manner previouslydescribed. Upon the operation of relay 117, the automatic selector switch G advances until the brush a," V

engages the contact to which signal control conductor Al, temporarily grounded, is connected, when relay 32 operates. Relay 120 then operates to deenergize relays 117 and 118, the deenergization of the latter causing the energization and locking up of relay 124. The operation of relay 32 causes the energization of the release magnet SRM, whereupon the sending clistributer S transmits over the common conductor P a com Y bination of impulses determined by the polarities connected with the individualsending segments 1 to 6, by the brushes 1 to 6, respectively. The receiving distributor R at the office X functions, upon the reception of the transmitted combination of impulses by the relay 25, tocause the temporary deenergiZ-ation of relay 82 and temporary energization of relays 43, 51 and 52, whereby sig nal receiving relay 77 is energized and locked up. Marginal relay 72 then operates to light the supervisory lamp 131. Relay? 5 is deenergized upon the operation of signal receiving relay 77.

The closure of the switchhoolr contact shortly after the opening thereof causes the deenergization of the supervisory relay 94. Relay 119 is immediately deenergized and relay 1 1-6 energized. Then, upon the energization of the supervisory relay 9st, in response to the next opening of the switchhook contact relays 1 7, 118 and 119 operate in the order named, as before described. Upon the operation of relay 118, relay 122 is energized over a circuit from battery through the right-hand alternate contact of signal receiving relay 85, winding and righthand normal contacts of relay 122, left-hand alternate contact of relay 12 1 and the righthand alternate contact of relay 118 to ground. Relay 122 immediately locks up through its rigl1tl1and alternate contact and the lefthand normal contact of relay 121 to ground. Upon the energization of relay 122, relay 119 is locked up over a circuit from battery, through the *inding of relay 119, alternate contact thereof, midd e alternate contact of relay 122, and the left-hand normal contact of relay 121 to ground, whereby relay 119 is removed from the control of the supervisory relay 941, during the rapid energization and deenergization thereof, while the switchhook contact is being rapidly opened and closed to signal the operator at the ethos X. The energization of relays 11'? and 118 causes the automatic selector switch G to start the sending c istributer b which transmits over the conductor the combination of impulses corresponding to trunk line L1, and determined by the brush 6;, connecting with the temporarily grounded signal control conductor Al. I

Upon the reception of these impulses by the relay 25 at ofiice X, the receiving distributer functions again to cause the temporary deenergization of relay 82 and the temporary energization of relays 13, 51 and 52 as before. \Vhen the brush 10 engages segments 20 and 21, signal receiving relay 98 operates over a circuit from the negative battery 86 through the normal contact of relay 4-6, segment 20, brush 10, segment 21, lower normal contacts of relays 45 and 50, lower alternate contact of relay 51, upper normal contacts of relays 53 and 58, signal receiving conductor E, contact of relay 75 and the left-hand winding of relay 98 to ground. Relay 98, in operating completes a locking circuit for itse f from battery, through the contact of relay 7 8 and the right-hand winding and right-hand alternate contact of relay 98 to ground. The operation of relay 98 connects an interrupter 97 in circuit with resistance 130, thereby substituting an interrupted ground V for the continuous ground, which causes the intermittent operation of the marginal relay 72. The intermittent operation of relay 72 causes the intermittent lighting of the supervisory lamp 131 which serves as a recall signal to the operator at the office X, while the switchhook contact may be rapidly opened and closed many times but afterthe second opening the only effect produced upon the apparatus associated with thetrunk lineLl is th'eenergization and de energization of the supervisory relay 94: and no apparatus associated with the common signaling conductor P is affected thereby. Therefore when the called subscriber recalls,

only two combinations of impulses, or two signals are transmitted over the conductor to cause the intermittent l1ght1ng of the su )ervisor 1 lam 3 at the office X. This in termittent lighting is at a constant rate,

while the rate at which switchhook contact relay 9 l is deenergized. After the comparatively extended deen'ergization of this supervisory relay 94, relay 116 releases its armatures and upon the closure of its normal contact relays 117 and 121 operate over a circuit from batterythroughthe winding "of relay 117, left-hand contact of relay 120, winding of relay121, right-hand normal contact of relay 118,right-hand alternate contact of relay 124, normal contact of relay 116 and the normal contact of supervisory relay 94; to -ground. The energization of therelay 121 releases relays 119, 122, 123 and 12 1. The operation of relay 121 also grounds the signal control conductor (Y1, and the operation of relay 117 causes the energization of start magnet30. The selector switch G thereupon functions and the brushes thereof are advanced step-bystep until brush a engages the contact to which jthe grounded signal control conductor (1'1 is connected. Thenthe control apparatus associated with the selector G and sending distributer S function to cause the sending distributer S to transmit the same con bin-ation of impulses transmitted at the time the receiver was removed from the switchhook when the subscriber responded to theoperation of the call bell; .The reception of the'transmitted impulses at the oiiice X causes the transmission of a positive impulse from the positive battery 99over the signal receivingconductor Elior differentializing signal receiving relays 77 and 98 whereby these two relays release their armatures disconnecting the interrupter 97 from circuit relation with the marginalrelay 72. The relay 72 thereupon opens its contact extinguishing the supervisory lamp ,131. Relay 75 operates upon the deenergization of relay 77. r

If, after repeatedly opening and closing the switchhook contact to signal theoperator at the ofiice X, the subscriber at thestation on line N should leave the switchhook contact open, as whenthe receiver is restored to the switchhook, supervisory relay 94 would be energized, An extended energiza tion of the supervisory relay 9 1 causes the cleenergization or the relay 1 16 which upon the'closure of its normal contact causes the energization of relays 117 and 121 over a circuit from battery'through the winding of -relay-117, left-hand contact of relay 120,

windingof relay i121, right-hand normal contact of relay 11 8, right-hand alternate contact of relay 12a, left-handalternate con tact of relay 122 and the contact of relay 146 .to ground. The selector switch G and the sending and receiving distributers S and R thereupon function in the manner previously described for causing the difierentialization and release of the signal receiving relays 77 and 98 which in releasing disconnect theinterrupter'97 from circuit relation with marginal relay 72. Following the release ofthe relay 121, brought-about in the manner before described, upon the energization'of relay 120, relays 117 and-118 are operatedover a circuit from battery through the winding or" relay 117, left-'handcontact otrelay 120,

winding and left-hand normal contact of ,relays118, left-hand normal contactof relay 119, right hand contact of relay 120, righthand normal contact of relay 121 and the alternate contact of supervisory'relay Qtto ground. Relays 117 and 118 are locked up immediately upon the energization of relay 118' and relay 119 operates shortly -after the energization of relay 118 to openthe original energizing circuit ofrelay 118 v The energization of relays 117 and 118 results in the operation of the selector switch G and the sending and receiving distributer S5 and R for sendingand receivinga combination of impulses corresponding to'the polarities connected with the individual sending segments 1 to Gby means ofthe'brushes 1 to 6, the polarities being those connected with the first contacts of the first six levels on switch G allotted to trunk line L1. Upon the reception of these impulses by'the relay 25, the receiving distributer R functionsto cause the energization and locking up of signal receiving relay 77, whereupon marginal relay 72 operates to light the supervisory lamp 131 which now serves asa disconnect signal to the operator at the ofiice X.

Operator at ofiice X disconnects one card circuit from and connects another cord circuit with trunk Zinc L].

If after the connection has been estab lished between the cord circuit and thetelephone line, by way of the trunk line L1, and the toll switching trunk circuit M, shouldit be found that the connected cord circuit is noisy, the subscriber on line N may signal the operator at oiiice X, by causing the intermittent operation of the supervisory-lamp 131 in the manner hereinbefore described.

The operator at oflice X, after observing the intermittent lighting of the supervisory lamp, may connect the usual operators telephone set (not shown) with the engaged cord circuit and converse with the subscriber jack 71,. relay 78 is deenergized in precisely the same manner as when the ringing-hey is actuated, so that, it provision were not made to prevent it, ringing current would be applied to the line of subscriber N when the second plug is inserted-into thejack 71. In

order to prevent this false application of ringing current to the distant connected called line, the energizing circuit of the relay lay 7 6" includes an alternate contact. ofrelay 7 1 and is locked up immediately upon energization, so that when the plug is withdrawn from the ack 71, relay 7 1 is d'eenergized and cannot be. energized again until after the deenergization of relay76.

' The sequence of operations resulting from the withdrawal of the plug from the jack 71 and the insertion of another plug therein;

Upon the with will now be described. A drawal of the plug from the jack 71, relays 73, 74, 75 and 78 are released. Upon the "release of relay 74, the start magnet 30 is energized, whereupon motor magnet Mhi advances the brushes of the automatic selector switch G until brush a engages the contact "to which the grounded signal control conductor C1 is connected. Relay 32 thereupon operates, following which relay 76 isdif- '74 includes thej'normally closed contact of 1 relay 76, while the energizing circuitoi re V ferentialized and releases its armatures. As a result of the operation of the relay 82, the. sending distributer S transmits a combination of impulses or code signal which, upon being received by the differential polar-. ized relay 25 at the office Y causes the functioning of the receiving distributer R. Relay 82 is thereupon temporarily deenergized and relays 43, 46, 51 and 52 temporarily energized, so that when the brush 10 engages the segments 20 and 21, a positive impulse from the positive battery 99 is transmitted over the circuit including the right-hand winding of signal receiving relay 85. Relay 85 is thereby difi'erentialized and releases its armatures, closing the circuit of and lighting the supervisory lamp 90. Immediately after the withdrawal of one plug from the jack 71, another plug is inserted therein,: so that relays 7 3 and 75 are immediately energized. Relay 74, however, does not operate unless relay 76 has been previously deenergized in the manner before described or until relay 76 is deenergized.

The energization of relay 7 4 causes the energization and locking up of relay 76, while relay 74, upon being energized locks up through one of its alternate contacts. Upon the energization of relay 74 magnet 30 operates to close the circuit of the motor magnet MM which thereupon advances the brushes of the automatic selector switch Guntil the brush a engages the contact to which the signal control conductor A1 is connected. Relay 32 then operates in the manner before described causing relay 78 to operate and lock up. The sending distributer S transmits over the signal conductor P a combination of impulses which, through the operation of the receiving distributer R, causes the transmission of the negative impulse from battery 86 over a circuit including the left-hand winding of signal receiving relay 85. Relay 85 is thereupon energized and locks up, opening the circuit of supervisory lamp 90, whereupon all apparatus is restored to the condition existing prior to the removal of the plug from the jack 71. The described operations follow each other so closely that the lamp 90 is lighted for a very brief interval.

The operations described above with reference to building up a connection over the trunk line L1 with the telephone line N and the breaking down of such a connection are characteristic of those taking place in building up and breaking down a connection over any one of the trunk lines to'which the signaling )ath P is common. The only essential di erence in operation, so far as the establishment of connections over the different trunk lines is concerned, is that different code signals are, employed for the different trunk lines, and while this invenserved by the same common signaling path.

Signals from oificeXto ofiice Y. Signals ggggg l i ii Guard. Ring. D3563?" b ri Rebewer Flashing.

No. hook. hook. v

In this table, the numbers in the first column indicate the numbers assigned to the trunk lines, while the numbers in the remaining columns indicate the order of the impulses of each group of six; The numher 3 appearingin the first line in the second,'third, fifth and seventh columnsof the table means that the third impulse to be transmitted is negative, while .the'numbers 36 appearing in the fourth and sixth columns means that the third and sixth imlevels of the automatic selector switches Gr and Gr.

lVhat is claimed is:

1. In a telephonesystem, in combination, a plurality of trunk lines and a signaling path common thereto extending between two stations, means at one station for transmitting over the signaling path code signals individual to the different trunk lines, a normally inactive switching device common to the trunk lines for determining the codes of the signals to be transmitted, and means controlled by a change in condition on any one of the trunk lines for rendering the switching device active.

2. In a telephone system, in combination, a plurality of trunk lines and a signaling path common thereto extending between two stations, means at one station for transmitting over the signaling path code signals individual to the different trunk lines, a switching device common to the trunk lines for determining the codes of the signals to be transmitted and comprising a plurality of sets of stationary contacts and a cooperating movable contact for each set, and means controlled by a change in condition on any one of the trunk lines for advancing the movable contacts into engagement with certain of the stationary contacts determined by the trunk line on which the change occurs for determining the code of the signal to be transmitted.

3. In a telephone system, in combination,

a plurality of trunk lines and a signaling path common thereto extending between two stations,'sending means at one station for transmitting over the signaling path code signals individual to the different trunk lines, a switching device common to the trunk lines comprising sets of stationary contacts and a cooperating movable contact for each set, and means controlled by a. 7 change in condition of any one of the trunk lines for advancing the movable contacts into engagement with certain of the stationary contacts jointly determined by the character of the change and the trunk line in which the change occurs and responsive to a subsequent change in condition of the same trunk line for causing the movable contacts to engage other stationary contacts determined by the character of the subsequent change. 7

4. In a telephone system, in combination, a plurality of trunk lines and a signaling path common thereto extending between two stations, a sending distributer at one line.

5. In a telephone system,in combination, a plurality of trunk lines and a signaling path common thereto extending between two stations, a sending device having individual sending contacts for transmitting over the signaling path code signals individual to the different trunk lines, each code signal comprising a plurality of current impulses equal in number to the number of individual sending contacts, a switching device having a plurality of sets of stationary contacts and a movable contact for each set connected with the individual sending contacts, and means controlled by each trunk line for causing the movable contacts to come to rest in engagement with certain of the stationary contacts determined by the controlling trunk line.

6. In a telephone system, in combination, a plurality of trunk lines and a signaling path common thereto extending between two stations, a sending device at one station for transmitting over the signaling path code signals individual to the different trunk stationary contacts individual to the con trolling trunk line and determined by the character of the change in condition of the control-ling trunk line for determining the code of the signal to be transmitted.

In witness whereof we hereunto subscribe our names this 28th day of July, A. D. 1919.

l-IARRY lV. MAoDOUGAL. HUGH D. MAOPHERSON. 

